1. Field of the Invention
The present invention relates to a cosmetic composition and more particularly, to a cosmetic composition for skin whitening comprising senkyunolide A as an active ingredient and its applications.
2. Description of the Related Art
Colors of human skin, hair and iris are ascribed to melanin, keratin and hemoglobin. The melanin has been considered as a pivotal factor for skin color and the color of skin is determined depending on the amount, disposition and distribution of melanin.
The major factor of skin-darkening is over-expression of melanin. UV-irradiated epidermal keratinocytes secrete melanin-inducing factors resulting in synthesis of melanin from activated dermal melanocytes and the secreted melanin on epidermis pigments the skin.
Detail mechanism of melanin synthesis has been investigated. In an activated melanocyte, tyrosinase converts tyrosine into dopaquinone and its oxidized derivative, dopachrome, is consecutively oxidized into 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA). The final copolymerization of the DHI and DHICA forms melanin.
Currently, most inhibitors of melanin synthesis target the tyrosinase. Well-known tyrosinase inhibitors are kojic acid, albutin, hydroquinone, vitamin C and extracts of various natural materials.
Recent years saw dramatic investigations both in terms of interrelation of keratinocyte and melanocyte, and cytokines secreted by keratinocytes. Among them, the roles of endothelin, prostaglandin, nitric oxide and melanocyte-stimulating hormone (MSH) in activation of melanocytes leading to melanogenesis have been reported several times.
Therefore, the present inventors have been endeavored to alleviate the melanin-inducing stimuli such as UV irradiation and to inhibit the UV-derived physiological activity and synthesis of melanin-inducing factors. In particular, the present inventors gave a due investigation on candidate substances enabling to inhibit melanin synthesis induced by melanocyte-stimulating hormone (MSH).
α-melanocyte stimulating hormone (αMSH) expressed by UV irradiation or pregnancy binds to its receptor on melanocyte leading to increase of melanin via activation of melanocyte, tyrosinase and melanocyte dendrite. Consequently, it is highly probable to gain skin-whitening effect and alleviation of pigmentation by inhibiting αMSH. For that reason, the need of inhibitors for α MSH has been highly rising in the art.